Method and apparatus for detecting pedestrian vehicle impact

ABSTRACT

An apparatus ( 50 ) detects a pedestrian/vehicle impact, the apparatus including a plurality of sensors ( 62, 64, 66 ) mounted near a forward location of a vehicle ( 52 ), each sensor providing an associated signal indicative of an impact event. A metric determining device ( 80 ) determines metric values for each of the sensor signals. A controller ( 80 ) determines if any of said determined metric values indicates the occurrence of a misuse event. The controller also determines if a pedestrian/vehicle impact event is occurring by comparing the metric value of at least one sensor signal against a selectable threshold. An actuation signal is provided in response to the comparison. The selectable threshold is selected in response to the determined occurrence of a misuse event. An actuatable pedestrian impact mitigation device ( 84 ) is attached to the vehicle and is actuated in responsive to the actuation signal from said controller.

TECHNICAL FIELD

The present invention relates to a protection system and, moreparticularly, to a method and apparatus for detecting a pedestrianvehicle impact.

BACKGROUND OF THE INVENTION

Vehicle occupant protection devices for helping to protect a vehicleoccupant during a vehicle event such as a crash, roll-over, etc., areknown. To detect such a vehicle event, one or more event sensors aremounted to the vehicle and provide signals indicative of vehicle eventconditions for which actuation of the protection device may be desired.The event sensors are connected to a controller that evaluates the eventsensor signals using appropriate metrics. Upon determining theoccurrence of a particular type of vehicle event, the vehicle occupantprotection devices, e.g., air bags, inflatable side curtains, etc., areactuated.

Pedestrian protection systems have been proposed to reduce pedestrianinjury when struck by a moving vehicle. Some proposed pedestrianprotection systems include a sensor mounted in the vehicle bumper. Ifthe sensor detects an impact with a pedestrian, an actuatable device isactuated to mitigate the impact effect. Such actuatable devices include,for example, actuators to raise the trailing end of the hood upward soas to aid in absorbing the impact effect. Actuatable forward mounted airbags have also been proposed to reduce impact effects.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus areprovided for determining a vehicle/pedestrian impact using forwardmounted accelerometers and analyzing signals from the accelerometers interms of impact energy.

In accordance with one example embodiment of the present invention, anapparatus detects a pedestrian/vehicle impact comprising a plurality ofsensors mounted near a forward location of a vehicle, each sensorproviding an associated signal indicative of an impact event. A metricdetermining device determines displacement and impact energy metricvalues for each of the sensor signals and a controller determines if apedestrian impact has occurred in response to the determined metricvalues and provides an actuation control signal in response thereto. Anactuatable impact mitigation device is attached to the vehicle and isresponsive to the actuation control signal.

In accordance with one example embodiment of the present invention, anapparatus detects a pedestrian/vehicle impact, the apparatus including aplurality of sensors mounted near a forward location of a vehicle, eachsensor providing an associated signal indicative of an impact event. Ametric determining device determines metric values for each of thesensor signals. A controller determines if any of said determined metricvalues indicates the occurrence of a misuse event. The controller alsodetermines if a pedestrian/vehicle impact event is occurring bycomparing the metric value of at least one sensor signal against aselectable threshold. An actuation signal is provided in response to thecomparison. The selectable threshold is selected in response to thedetermined occurrence of a misuse event. An actuatable impact mitigationdevice is attached to the vehicle and is actuated in responsive to theactuation signal from said controller.

In accordance with another example embodiment of the present invention,a method is provided for detecting a pedestrian/vehicle impactcomprising the steps of sensing impacts near a forward location of avehicle and providing an associated signal indicative of an impactevent, determining displacement and impact energy metric values for eachof the sensor signals, determining if a pedestrian impact has occurredin response to the determined metric values and providing an actuationsignal in response thereto, and actuating an actuatable impactmitigation device in response to said actuation signal.

In accordance with another example embodiment of the present invention,a method is provided for detecting a pedestrian/vehicle impactcomprising the steps of sensing impact acceleration at a a plurality oflocations near the front of the vehicle, determining metric values foreach of the sensed accelerations, and determining if any of the metricvalues indicates the occurrence of a misuse event. The method furtherincludes the steps of selecting a threshold in response to thedetermination of the occurrence of a misuse event, comparing the metricvalue of at least one sensed acceleration against the selectablethreshold, and providing an actuation signal to an impact mitigationdevice in response to said comparison.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention willbecome apparent to one skilled in the art upon consideration of thefollowing description of an exemplary embodiment of the invention andthe accompanying drawings, in which:

FIGS. 1A and 1B illustrate a pedestrian impact detection device inaccordance with an exemplary embodiment of the present invention showingtwo different mounting arrangements for sensors;

FIG. 2 is a block diagram showing a portion of the control logic used bythe electronic control unit of FIG. 1A in accordance with an exemplaryembodiment of the present invention;

FIG. 3 is a block diagram showing a portion of the control logic used bythe electronic control unit of FIG. 1A in accordance with an exemplaryembodiment of the present invention;

FIGS. 4 and 5 are block diagrams showing portions of the discriminationcontrol logic followed by the electronic control unit of FIG. 1A inaccordance with an exemplary embodiment of the present invention;

FIGS. 4-13 are block diagrams showing portions of the discriminationcontrol logic followed by the electronic control unit of FIG. 1A duringdifferent type of impact events in accordance with an exemplaryembodiment of the present invention;

FIGS. 14-17 are block diagrams showing portions of the discriminationcontrol logic followed by the electronic control unit of FIG. 1A inaccordance with an exemplary embodiment of the present invention; and

FIG. 18 is a block diagram showing a portion of the control logic of theelectronic control unit for determining metric values in accordance withan exemplary embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Referring to FIGS. 1A and 1B, a detection apparatus 50 is provided fordetecting a pedestrian/vehicle impact. The detection apparatus 50 ismounted in a vehicle 52 and includes a plurality of sensors 54 mountednear a forward location of the vehicle. In accordance with one exampleembodiment of the present invention shown specifically in FIG. 1A, aplurality of sensors 62, 64, and 66 are mounted to a forwardcross-member 68 of the vehicle 52 so as to be positioned at the leftfront location, center front location, and right front location,respectively, of the vehicle 52. In accordance with another exampleembodiment of the present invention, shown in FIG. 1B, a plurality ofsensors 72, 74, and 76 are mounted to a front bumper 78 of the vehicle52′ so as to be positioned at the left front location, center frontlocation, and right front location, respectively, of the vehicle 52′.The operation of the invention is the same for either sensor mountinglocation so only one mounting arrangement, i.e., FIG. 1A, is discussedin detail, it being understood that the invention with the othermounting location works similarly. The sensors, 62, 64, 66 (and sensors72, 74, 76) are accelerometers that each provide an associatedelectrical signal having electrical characteristics (e.g., frequency,amplitude, etc.) indicative of an impact event between the vehicle andan object such as a pedestrian. In accordance with one exampleembodiment, the sensors have their axis of sensitivity oriented to beparallel to the front-to-rear axis of the vehicle 52.

Each of the sensors 62, 64, 66 are connected to an electronic controlunit (“ECU”) 80 for monitoring and processing the accelerometer signals.The ECU 80 may be a microcontroller, a microprocessor, discretecircuitry, and/or an application specific integrated circuit (“ASIC”)designed to function in accordance with the present invention. The ECU80 may be located within the vehicle cabin or other vehicle area andconnected to the accelerometers via a communication bus or other wiringarrangement or even wirelessly.

A vehicle speed sensor 82 is also connected to the ECU 80 so as toprovide a vehicle speed signal to the ECU 80. The ECU 80 is furtherconnected to an actuatable pedestrian impact mitigation device 84 suchas actuators 86, 88 located at the trailing end of the vehicle hood 90so that, when actuated by the ECU 80, the actuators lift the trailingend of the hood upward thereby allowing the hood to mitigate pedestrianinjury during an impact event. The actuators can be actuatable via, forexample, pyrotechnics. Other means for actuating the actuators 86, 88are also contemplated. Also, rather than hood actuators for pedestrianimpact mitigation, other actuatable devices could be used such asforward mounted air bags.

Referring to FIG. 2, the control logic performed by the ECU 80, inaccordance with an example embodiment of the present invention, is shownto determine if there is a pedestrian vehicle impact occurring to theleft side of the vehicle 52. The vehicle speed signal from the vehiclespeed sensor 82 is monitored by the ECU 80 and one of a plurality ofsets of velocity threshold values are selected in response to themonitored vehicle speed value. In accordance with one example embodimentof the present invention, the vehicle speed being between a minimumvehicle speed value 102 and a maximum speed value 104 is classified byvelocity range classifier logic (“VRCL”) 116 of the ECU 80 as fallingwithin, for example, one of three specific speed ranges. The speedvalues that define adjacent speed ranges may overlap. Each speed rangehas associated therewith, a set of threshold values that are used in thecontrol process performed by the ECU 80 for deciding whether to actuatethe actuatable impact mitigation devices. If the monitored vehicle speedis less than a minimum vehicle speed 102, for example 20 KPH, or if themonitored vehicle speed is greater than the maximum vehicle speed 104,for example 50 KPH, the ECU 80 will not permit actuation of theactuatable pedestrian impact mitigation device 84. Therefore, it shouldbe appreciated that each of the speed ranges used for possible actuationfall between the minimum 102 and maximum 104 speed values.

As mentioned, the vehicle speed between the minimum vehicle speed 102and the maximum vehicle speed 104 is classified or determined as fallinginto one of the predetermined number of discrete speed ranges, e.g., alow-velocity range 110, a mid-velocity range 112, or a high velocityrange 114. The mid-velocity range 112 values and the low-velocity range110 values can have overlapping velocity values, and the mid-velocityrange 112 values and the high-velocity range 114 values can haveoverlapping velocity values. The classification of the monitored vehiclevelocity value into one of the velocity ranges by the velocity rangeclassifier logic 116 establishes the threshold value set used in laterlogic processing described below. If the vehicle speed falls in anoverlap velocity range area, threshold sets from each of the velocityranges are used by the ECU 80 in its discrimination determinationprocess with the results of the determinations being logically OR'ed.The threshold value set(s) selected in response to the velocity rangeclassifier logic 116 is used in a discrimination determination functionof the ECU 80.

The ECU 80 determines acceleration metric values for each of the sensors62, 64, and 66 using metric computation functions 130, 132, 134,respectively. Each accelerometer output signal is monitor and associateddisplacement values are determined. Specifically, two displacementvalues are determined from acceleration moving average values occurringover two different time widows. The first determined acceleration movingaverage value over the first time window is referred to as A_MA_1. Thesecond determined acceleration moving average value over the second timewindow is referred to as A_MA_2. Displacement values are determined(double integral of acceleration) from each A_MA_1 and A_MA_2 values ina manner described below with regard to FIG. 18. In addition todetermining two displacement values for each acceleration signal, animpact energy value is determined from the sensor signal. The determinedimpact energy is based on the sensor signal within a predeterminedfrequency range. As will be described in detail below, thediscrimination logic 120 compares each of the determined displacementmetric value as a function of the impact energy against the thresholdsets established by the velocity range classifier logic 116. The outputof the discrimination logic 120 is connected to one input of a logic ANDfunction 140 through a latch 141.

In the discrimination logic 120, each of the two determined displacementmetric values as a function of impact energy are compared against athreshold set (two threshold sets if the vehicle speed falls within anoverlap portion of the speed ranges) selected from the velocity rangeclassifier logic 116 and the resulted comparisons are logically OR'ed.If the vehicle velocity value does fall within overlapped speed ranges,the comparisons of displacement as a function of impact energy againstthe threshold sets from both speed ranges are logically OR'ed.

In another portion of the control logic shown in FIG. 2, the outputsignals from each of the other two accelerometer 64 and 66 are processedby associated metric computation functions 132, 134, respectively. Thevalues determined by the metric computation functions 132, 134, such asmoving average values of the acceleration signals, are compared againstassociated fixed thresholds to determine if an impact event above apredetermined value is sensed. The output of the resultant comparisonsof the comparisons performed in the metric computation functions 132,134 are connected to a logic OR function 144. The output of the logic ORfunction 144 represents a safing function determination for a pedestrianimpact event. The result or output of the safing determination 146 isconnected to the second input of the logical AND function 140. Theoutput of the logic AND function 140 represents a system response forleft impacts 150

FIG. 2 shows the left impact sensing control logic. Similar controllogic is present within the ECU 80 for center impact sensing and rightimpact sensing. In the center impact sensing logic, the ECU 80 uses thecenter sensor signal as a discrimination signal and the right and leftsensor signals as safing signals. In the right impact sensing logic, theECU 80 uses the right sensor signal as a discrimination signal and theleft and center sensor signals as safing signals.

Referring to FIG. 3, the system response for center impact is shown as152 and the system response for right impact is shown as 154. Each ofthe system response determinations for left 150, center 152, and right154 are connected to a logic OR function 156 of the ECU 80. The outputof the logical OR function 156 represents the final system response 158that results in the ECU controlling the actuatable pedestrian impactmitigation device 84. If the system response 158 is TRUE or HIGH,meaning that a pedestrian impact has been determined, the actuatablepedestrian impact migration device 84 is actuated.

Referring to FIG. 4, the discrimination determination logic for a leftimpact sensor using the determined displacement value based on one ofthe acceleration time windows, i.e., A_MA_1, as a function of impactenergy determined from that sensor is shown. The displacement calculatedvalue from metric computation function 130 as a function of impactenergy is compared against a threshold set 160. The selection of thethreshold set 160 is controlled by the velocity range classifier logic116. Each threshold set 160 includes a normal threshold value and a highthreshold value. The high threshold value is a threshold value that isgreater than the normal threshold value. The normal and high thresholdvalues can either be fixed values or can be variable values. For thepurpose of explanation, each the normal and high threshold values aredescribed as being fixed values. Again, the threshold value set selectedin the discrimination determination shown in FIG. 4 is selected inresponse to the vehicle velocity value falling within a particular speedrange as determined by the velocity range classifier logic 116. If thespeed falls within an overlap portion of the ranges, comparisons withtwo sets of normal and high thresholds will be performed with theresults logically OR'ed.

Assuming that the vehicle speed falls within a speed range that is notoverlapped by another speed range, only one of the comparisons of thedisplacement as a function of impact energy is used in thediscrimination determination. Whether the normal or high threshold isused is responsive to a misuse determination using misuse determininglogic 170. A misuse condition is defined as a predetermined range ofsensed displacement as a function of impact energy values that couldoccur for non-pedestrian impacts such as a rock hitting the front of thevehicle, etc. Under such misuse impact event, it would not be desirableto actuate the actuatable pedestrian impact mitigation device 84.

Referring to FIGS. 4 and 6, the misuse determining logic 170 processesthe output signals from each of the sensors 62, 64, 66 to determine ifeach of the sensors indicate that a misuse event has occurred.Specifically, the metric values from the left sensor 62 are comparedagainst misuse values in misuse logic 172. The metric values from thecenter sensor 64 are compared against misuse values in misuse logic 174.The metric values from the right sensor 66 are compared against misusevalues in misuse logic 176. The misuse event boxes are seen in FIG. 6.If the associated sensor signal falls within a misuse box, the output ofthe logic 172, 174, 176 will be TRUE or HIGH. The outputs from themisuse determination functions 172, 174, and 176 are logically AND'ed at178 by the ECU 80. The output of the AND function 178 is latched by atime latch 180. The output of the latch 180 is used to control aselector function 184.

The selector function 184 will either select the normal thresholddetermination 162 or the high threshold determination 164 in response tothe output of the latch 180, which is, in turn, responsive to whether amisuse event has occurred. If a misuse event has occurred, the output oflatch 180 will be TRUE or HIGH and the resultant comparison using thehigh threshold 164 is output to the discrimination status condition 186.If no misuse event has occurred, the output of the latch 180 will beFALSE or LOW, and the resultant comparison using the normal threshold162 is output to the discrimination status 186. The discriminationstatus left 186 is used by the discrimination logic 120.

Referring to FIG. 5, the control logic, similar to that shown in FIG. 4for the A_MA_1 left impact determination, is shown for the left sensorimpact determination using the A_MA_2 time window for displacementdetermination.

One should appreciate that overall control logic duplicates the controllogic shown in FIGS. 4 and 5 for each of the sensors 62, 64, and 66.Also, the duplicated control logic shown in FIGS. 4 and 5 areincorporated into the control logic shown in FIG. 2 and that the controllogic shown in FIG. 2 is duplicated for the other sensors to end up withthe final control arrangement shown in FIG. 3 that produces a finalsystem response to actuate or not actuate the actuatable pedestrianimpact mitigation device 84.

Referring to FIG. 18, the determination metric calculations will beappreciated. Each of the sensors 62, 64, 68 are accelerometers thatoutput an electrical signal having electrical characteristics such asfrequency and amplitude indicative of the impact. Each sensor has itsown associated metric calculation to determine displacement values overtwo different time windows and the impact energy value based on impactenergy over a particular frequency range. The controller 80 performseach of these metric calculations. By way of example, the processing foraccelerometer 62 is shown to determine displacement values and impactenergy, it being understood that the processing for the otheraccelerometers 64, 66 is the same. The output signal from theaccelerometer 62 is low-pass filtered using, for example, a hardwarefilter 200 to permit further process (anti-alias filter). The low-passfilter passes a first frequency band, e.g., frequencies from 0-800 Hz.The filtered signal is converted to a digital signal using ananalog-to-digital converter 202 for further processing by the ECU 80.The ECU 80 then high-pass filters 204 the signal so as to remove anysensor bias (DC drift). The high-passed signal is then further high-passfiltered 206 to eliminate frequencies from DC-400 Hz. The output of HPF206 will then contain frequency values between 400-800 Hz. The HPF 206also eliminates rough road events from further processing. A secondhigh-pass filter 207 is cascaded with the first high-pass filter 206 toform a second order filter to obtain a sharper cutoff. The absolutevalue 210 of the high-pass filtered 206 signal is determined. Theabsolute value of the filter acceleration signal is indicative of theimpact energy as sensed by left sensor 62. A moving average A_MA of theabsolute value of the signal is determined 211 for smoothing purposes.The resultant signal is a high-pass filter signal 220, designated HPF_2,and is indicative of impact energy within a particular frequency range(e.g., 400-800 Hz) of interest. This HPF_2 impact energy value is usefulin determining the occurrence of a pedestrian impact.

The output of the filter 204 is also used to determine displacementvalues (double integral of acceleration) over two different timewindows. Specifically, the output of the HPF 204 is low-passed filteredby a low-pass filter 208 so as to pass signals with a frequency betweenDC and 220 Hz, for example. The output of the LPF 208 is processed by afirst moving average calculation 230 (first integral) followed by asecond moving average calculation 232 (second integral) to arrive at afirst displacement value 234 which is designated Displacement_1. Theoutput of the LPF 208 is also processed by a moving average calculation240 (first integral) followed by a moving average calculation 242(second integral) to arrive at a second displacement value 244 which isdesignated Displacement_2. The time windows for the moving averagecalculations for Displacement_1 and Displacement_2 are different.

Again, it should be appreciated that the two displacement values andimpact energy value are determined for each of the sensors 62, 64, 66.The electronic control unit 80 determines if a pedestrian impact eventis occurring by comparing the determined displacement values as afunction of the determined impact energy against threshold value sets.The selection of threshold value set comparison results are controlledin response to the determination of the occurrence of a misuse conditionas is explained below. It should be appreciated that the threshold setsused are based upon vehicle speed (determines which high and normalthreshold sets are used) and upon the determination of a misusecondition (use the high or the normal threshold).

FIG. 6, by way of example, shows the occurrence of a dynamic misusecondition based on metric 12 (displacement_1 as a function of impactenergy HPF_2) which would mean that the HIGH threshold determination 164would be selected. Since the determined displacement as a function ofimpact energy based on the left side accelerometer does not cross theHIGH threshold, the actuatable pedestrian impact mitigating device 84would not be actuated because of the impact sensed from that portion ofthe overall control logic. In effect, the system response 150 would be aFALSE or LOW. However, that system response 150 is OR'ed with the systemresponses 152, 154 for a final actuation determination. Also, thediscrimination determination shown in FIGS. 4 and 6 are based on thedisplacement A_MA_1 time window calculation. The final discriminationdetermination 120 is the result of OR'ing the A_MA_1 displacementdeterminations as a function of impact energy against thresholds withthe A_MA_2 displacement determinations as a function of impact energyanalysis.

Referring to FIG. 7, a static misuse impact event is shown as analyzedby a portion of the control logic based on the A_MA_1 signal using thediscrimination metric 12 logic (displacement_1 as a function of impactenergy HPF_2) of the discrimination logic 120 from the left sensor. Notethan no misuse box is entered so the normal threshold 162 determinationis selected. Since the normal threshold is not crossed in thedisplacement vs. impact energy determination, no activation would occuras a result of this analysis.

Referring to FIG. 8, a no fire pedestrian impact event is shown asanalyzed by a portion of the control logic based on the A_MA_1 signalusing the discrimination metric 12 (displacement_1 as a function ofimpact energy HPF_2) of the discrimination logic 120 from the leftsensor. Note than no misuse box is entered so the normal threshold 162determination is selected. Since the normal threshold is not crossed, noactivation would occur as a result of this analysis.

Referring to FIG. 9, a must fire pedestrian impact event is shown asanalyzed by a portion of the control logic based on the A_MA_1 signalusing the discrimination metric 12 logic (displacement_1 as a functionof impact energy HPF_2) of the discrimination logic 120 from the leftsensor. Note than no misuse box is entered so the normal threshold 162determination is selected. Since the normal threshold is crossed,activation of the actuatable impact mitigation device 84 would occur asa result of this analysis assuming the safing determinations are true.

Referring to FIG. 10, a dynamic misuse impact event is shown as analyzedby a portion of the control logic based on the A_MA_2 signal using thediscrimination metric 22 (displacement_2 as a function of impact energyHPF_2) of the discrimination logic 120 from the left sensor. Note thatthe misuse boxes are entered so that the logic selects the highthreshold for discrimination. Since the high threshold is not crossed,no activation would occur as a result of this analysis.

Referring to FIG. 11, a static misuse impact event is shown as analyzedby a portion of the control logic based on the A_MA_2 signal using thediscrimination metric 22 logic (displacement_2 as a function of impactenergy HPF_2) of the discrimination logic 120 from the left sensor. Notethan no misuse box is entered so the normal threshold determination isselected. Since the normal threshold is not crossed, no activation wouldoccur as a result of this analysis.

Referring to FIG. 12, a no fire pedestrian impact event is shown asanalyzed by a portion of the control logic based on the A_MA_2 signalusing the discrimination metric 22 logic (displacement_2 as a functionof impact energy HPF_2) of the discrimination logic 120 from the leftsensor. Note than no misuse box is entered so the normal thresholddetermination is selected. Since the normal threshold is not crossed, noactivation would occur as a result of this analysis.

Referring to FIG. 13, a must fire pedestrian impact event is shown asanalyzed by a portion of the control logic based on the A_MA_2 signalusing the discrimination metric 22 logic (displacement_2 as a functionof impact energy HPF_2) of the discrimination logic 120 from the leftsensor. Note than no misuse box is entered so the normal threshold 162determination is selected. Since the normal threshold is crossed,activation of the actuatable impact mitigation device 84 would occur asa result of this analysis assuming the safing determinations are true.

As mentioned, the discrimination logic shown and described in detail inFIGS. 4, 5, and 6 for the left sensor analysis is duplicated for thecenter sensor 64 and right sensor 66. FIGS. 14 and 15 show thediscrimination logic for the center sensor 64. FIGS. 16 and 17 show thediscrimination logic for the right sensor 66.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes and modifications within the skill of the art areintended to be covered by the appended claims.

1. An apparatus for detecting a pedestrian/vehicle impact comprising: aplurality of sensors mounted near a forward location of a vehicle, eachsensor providing an associated signal indicative of an impact event; ametric determining device for determining displacement and impact energymetric values for each of the sensor signals; a controller fordetermining if a pedestrian impact has occurred in response to thedetermined metric values and for providing an actuation control signalin response thereto; and an actuatable impact mitigation device attachedto the vehicle and being responsive to said actuation control signal. 2.The apparatus for detecting a pedestrian impact of claim 1 wherein saidmetric determining device determines impact energy from each sensor inresponse to sensor signals having frequency components within apredetermined frequency range.
 3. The apparatus for detecting apedestrian impact of claim 1 wherein said metric determining devicedetermines impact energy from each sensor in response to sensor signalshaving frequency components within a frequency range of 400-800 Hz. 4.The apparatus for detecting a pedestrian impact of claim 1 wherein saidmetric determining device determines displacement values from eachsensor over a predetermined time window.
 5. The apparatus for detectinga pedestrian impact of claim 1 wherein the metric values are comparedagainst selectable thresholds for determining occurrence of thepedestrian impact.
 6. The apparatus for detecting a pedestrian impact ofclaim 5 wherein the thresholds are selected in response to vehiclespeed.
 7. The apparatus for detecting a pedestrian impact of claim 5wherein the thresholds are selected in response to a misuse condition.8. An apparatus for detecting a pedestrian/vehicle impact comprising: aplurality of sensors mounted near a forward location of a vehicle, eachsensor providing an associated signal indicative of an impact event; ametric determining device for determining metric values for each of thesensor signals; a controller for determining if any of said determinedmetric values indicates the occurrence of a misuse event, saidcontroller further determining the occurrence of a pedestrian/vehicleimpact event by comparing the metric value of at least one sensor signalagainst a selectable threshold and providing an actuation signal inresponse to said comparison, the selectable threshold being selected inresponse to the determined occurrence of a misuse event; and anactuatable impact mitigation device attached to the vehicle and beingresponsive to said actuation signal from said controller.
 9. Theapparatus for detecting a pedestrian/vehicle impact of claim 8 furtherincluding a vehicle speed sensor for providing a vehicle speed signal,said controller determining the occurrence of a pedestrian/vehicleimpact in further response to said vehicle speed signal.
 10. Theapparatus for detecting a pedestrian/vehicle impact of claim 9 whereinsaid controller provides said actuation signal when said vehicle speedis greater than a first predetermined speed and less than a secondpredetermined speed.
 11. The apparatus for detecting apedestrian/vehicle impact of claim 8 wherein said plurality of sensorsare accelerometers.
 12. The apparatus for detecting a pedestrian/vehicleimpact of claim 11 wherein said metric determining device determinescrash displacement values for each of said sensors from said sensorsignals, said controller providing said actuation signal in response tosaid determined displacement values.
 13. The apparatus for detecting apedestrian/vehicle impact of claim 12 wherein said metric determiningdevice determines frequency content of each of said sensor signals, saidcontroller providing said actuation signal in response to saiddetermined displacement values as a function of the determined frequencycontent.
 14. The apparatus for detecting a pedestrian/vehicle impact ofclaim 13 wherein said misuse impact event is defined by a range ofdetermined displacement values as a function of a range of frequencyvalues, a determination of a impact event falling with both of themisuse ranges by the controller preventing provision of said actuationsignal for a predetermined time period.
 15. A method for detecting apedestrian/vehicle impact comprising the steps of: sensing impacts neara forward location of a vehicle and providing an associated signalindicative of an impact event; determining displacement and impactenergy metric values for each of the sensor signals; determining if apedestrian impact has occurred in response to the determined metricvalues and providing an actuation signal in response thereto; andactuating an actuatable impact mitigation device in response to saidactuation signal.
 16. The method of claim 15 wherein the step ofdetermining impact energy values is responsive to impact signals withina predetermined frequency range.
 17. A method for detecting apedestrian/vehicle impact comprising the steps of: sensing impactacceleration at a plurality of locations near the front of the vehicle;determining metric values for each of the sensed accelerations;determining if any of the metric values indicates the occurrence of amisuse impact event; selecting a threshold in response to thedetermination of the occurrence of a misuse impact event; comparing themetric value of at least one sensed acceleration against the selectablethreshold; and providing an actuation signal to an impact mitigationdevice in response to said comparison.
 18. The method of claim 17further including the steps of sensing vehicle speed, said step ofproviding the actuation signal being further response to the sensedvehicle speed.
 19. The method of claim 18 wherein step of providing theactuation signal is responsive to the sensed vehicle speed being greaterthan a first predetermined speed and less than a second predeterminedspeed.
 20. The method of claim 17 wherein the step of determining metricvalues includes the steps of determining crash displacement values foreach of said sensors from said sensor signals, said step of providingsaid actuation signal being response to said determined displacementvalues.
 21. The method of claim 20 wherein the step of determiningmetric values includes determining a high passed filtered accelerationvalue and wherein the step of providing the actuation signal is responseto said determined displacement values as a function of the high passedfiltered acceleration value.